John McCain!

A big win in South Carolina. Huckabee's down. But what about Mitt? Are we supposed to see McCain as big favorite now? Actually, it's not a great bet:

... Mitt Romney won the largely uncontested Nevada caucuses, giving him at least the claim of having won two contests in a row. On a more practical and potentially more meaningful level, he also captured more delegates on Saturday than Mr. McCain did.

... [McCain's] first two victories came in New Hampshire and South Carolina, where independents, who often seem more enthusiastic about Mr. McCain than members of his party do, are permitted to vote in the primaries.

The terrain from here is markedly different, starting Jan. 29 in Florida, where the Republican primary is open only to Republicans.

“He still has significant skepticism that he has to overcome in the Republican base,” said Gary L. Bauer, who sought the Republican presidential nomination in 2000 and is not endorsing anyone at this time. “The real test will be how well he can secure the Republican base as we head toward Super Tuesday.” Mr. Bauer added, “On balance, in most states, to get the nomination you’ve got to do very well among registered Republicans, and that is going to become increasingly important as other candidates drop out of the race.”

An exit poll in South Carolina offered evidence of the challenge Mr. McCain faces: 8 in 10 of the voters in the primary described themselves as Republicans, and just 3 in 10 of them voted for Mr. McCain. The finding suggests what Mr. McCain’s rivals were saying Saturday night: that he might not have won without the help of voters outside his party.

ADDED: Here's Noam Scheiber:

With John McCain's victory tonight, we've finally achieved that belated winnowing. In one quick burst, McCain has effectively knocked Mike Huckabee, Fred Thompson, and Rudy Giuliani from the race: Huckabee because it's not clear where he wins if he can't do it in as demographically favorable a state as South Carolina. (Fifty-nine percent of voters today were evangelicals; Huckabee only won them by a 40-27 margin over McCain.) Rudy because it's hard to see why anyone would perfer him to McCain going forward; both appeal to moderate, security-minded Republicans and McCain is the only one who hasn't been a disaster of late. And Thompson's finished--as if it needed to be said--because even he'd conceded this was his last chance to reverse a debilitating six-month slide. (One interesting sidenote: Huckabee's under-performance among evangelicals probably had something to do with the 15 percent of them Thompson picked off. I have a feeling that won't be Fred's last gift to McCain in this race...)

This is clearly a McCain-Romney race going forward. Romney has the money and may still be the establishment choice over McCain, who's widely disliked in elite GOP circles. The benefit of the latter will be, among other things, to dampen the fundraising boost McCain should receive from South Carolina.